The present invention relates to magnetic random access memory, and more specifically, to materials optimized for spin-torque memory using a magnesium oxide (MgO) tunnel barrier layer.
A spin torque magnetic random access memory (MRAM) device uses a two terminal spin-torque based memory element including a pinned layer, a tunnel barrier layer and a free layer in a magnetic tunnel junction (MTJ) stack. The magnetization of the pinned layer is fixed in a direction such that when current passes through the MTJ stack the free layer becomes either parallel or anti-parallel to the pinned layer. Resistance of the device depends on the relative orientation of the free layer and the pinned layers. Recent developments include the use of MgO based magnetic tunnel junction layers. A major problem with the development of a spin-transfer RAM in using MgO as a tunnel barrier layer within the MTJ stack is the amount of switching voltage required to switch the MTJ layer from a parallel state to an anti-parallel state. It is desired to reduce the amount of current needed to switch the device and make the switching reliable at any value of current and avoid read disturbances (i.e. when the device accidently switches due to a small read current).